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JOURNALS // Matematicheskii Sbornik // Archive

Mat. Sb., 1993 Volume 184, Number 2, Pages 129–144 (Mi sm968)

This article is cited in 10 papers

The problem of multiple interpolation in the half-plane in the class of analytic functions of finite order and normal type

K. G. Malyutin

Kharkiv State University

Abstract: The problem of multiple interpolation is considered in the class $[\rho(r),\infty)^+$ of functions of at most normal type for the proximate order $\rho(r)$ in the upper half-plane $C^+\colon f^{(k-1)}(a_n)=b_{n,k}$, $k = 1,\dots,q_n$, $n=1,2,\dots$, where the divisor $D=\{a_n,\,q_n\}$ has limit points only on the real axis, and the numbers $\{b_{n,k}\}$ satisfy the condition
$$ \varlimsup_{n\to\infty}r_n^{-\rho(r_n)}\ln\sup_{1\leqslant k\leqslant q_n}\dfrac{(\Lambda_n)^{k-1}|b_{n,k}|}{(k-1)!}<\infty. $$

The following result is valid.
Theorem. {\it $D$ is an interpolation divisor in the class $[\rho(r),\infty)^+$ if and only if
$$ \varlimsup_{n\to\infty}r_n^{-\rho(r_n)}\ln\frac{q_n!}{|E^{(q_n)}(a_n)|(\Lambda _n)^k}<\infty, $$
where $E(z)$ is the canonical product of the set $D$}.
Necessary and sufficient conditions are also found in terms of the measure determined by the divisor $D$: $\mu(G)=\sum_{a_n\in G}q_n\sin(\arg a_n)$.

UDC: 517.52

MSC: 30E05, 30D15

Received: 08.04.1991


 English version:
Russian Academy of Sciences. Sbornik. Mathematics, 1994, 78:1, 253–266

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